Process and device for producing press fittings from steel, in particular special steel

ABSTRACT

Special steel press fittings are produced in two process steps, which can be performed simultaneously, or also one after the other. The cut to size blank is widened in a die is upset in order to form the desired pipe connection areas.

This is a U.S. National Phase Application under 35 USC 371 ofInternational Application PCT/EP01/05547, filed on May 16, 2001.

FIELD OF THE INVENTION

Press fittings, which are used for connecting pipe ends with each otherand for making pipe junctions, have been increasingly employed forpipeline installations, for heating pipes as well as drinking waterinstallations, or for gas pipes. For making the pipe connection, pressfittings are pushed on the respective pipe ends, wherein an O-ring,which is maintained in an annular bead of the press fitting, makes afluid-tight connection. The press fitting is plastically deformedradially inward in a press area particularly provided for this, so thatit is mechanically secured on the pipe end. The connections obtained inthis manner can be dependably produced and are stable over a long time.

DESCRIPTION OF THE RELATED ART

Press fittings are required to be made from the same material as thematerial for the pipelines. Copper press fittings are used forinstallation on copper pipes. EP 0 649 689 B1 addresses the manufacture.Dies placed linearly and transversely, into which an appropriatelypreformed blank is inserted, are used for producing these copper pressfittings. In its interior shape, the die has an annular groove, whichfixes the exterior shape of an annular bead to be formed on the pressfitting. An upsetting device is used for forming this annular bead,which has a support mandrel which is inserted into the open pipe end ofthe blank lying in the die for support. To cause the wall material ofthe blank to flow into the annular groove, the upsetting device has afollow-up or upsetting sleeve, by means of which the pipe end in the dieis axially upset. In the process, the wall material of the press fittingflows plastically into the annular groove. In order to then dependablyembody the seat for the O-ring with the required precision, the supportmandrel and the follow-up sleeve are removed from the die, and aroller-burnishing process is performed. A rotatably seated rollermaintained on a finger is used for this, which is introduced into thepipe end and is pressed radially outward against the annular bead to beformed. The roller now performs a number of rotations, in the process ofwhich it rolls the corresponding annular bead.

This process is designed and suitable especially for producing copperpress fittings. It requires a blank, whose outer dimensions are matchedto the receiving chamber of the die, so that it rests snug against thedie. Therefore the blank must be given the appropriate rough shape priorto upsetting for the purpose of forming the annular bead. For thispurpose it must be widened in its end areas. This step must be takeninitially. Following the insertion of the pre-widened blank into thedie, it is cut to size. An upsetting and rough-burnishing step is thenperformed in the die on the pre-widened and length-calibrated (cut tosize) blank for creating the desired annular bead. Copper press fittingsare obtained, which have an annular bead which is set back in respect tothe pipe mouth. Pressing the press fittings is possible with appropriatepressing dies or pressing tongs, which simultaneously grasp the portionsof the fitting existing on both sides of the O-ring, so that even withthe use of copper as the fitting material a very good mechanicalconnection between the pipe end and the press fitting is obtained.

The dies for pressing the press fittings are specifically designed tothe special shape of the press fittings. In case of the use ofdifferently shaped press fittings, the respective pipe fitter mustobtain new dies.

As a rule, press fittings made of special steel for the installation ofspecial steel pipes are constructed in such a way that an O-ring seat isformed directly at their free end. A typical representative of suchpress fittings can be taken from EP 0 361 630 B1. This press fitting hasa connection section, whose interior diameter has been widened to theexterior diameter of a pipe to be connected. At the end of the pressfitting, its wall is initially bent radially outward, and is then beadedtoward the inside while forming an annular bead. Such press fittingscannot be pressed with the same dies, such as are already in use inconnection with copper press fittings having a pressing area on bothsides of the O-ring.

The manufacture of press fittings requires machines and processes, bymeans of which press fittings can be dependably produced in very largequantities. For producing dependable pipe connections, it is necessaryto produce the press fittings with very low tolerances. This must bepossible at manufacturing costs which are as low a possible.Accordingly, the machine or device for producing the press fittingsshould be designed to be simple and rugged, but still be able todependably produce press fittings of the desired quality.

SUMMARY OF THE INVENTION

Based on the foregoing, it is one object of the invention to create adevice and a process for producing press fittings, in particular made ofspecial steel, by means of which press fittings of the desired qualitycan be produced in a simple manner and with the required processdependability. Moreover, it is another object of the invention toproduce press fittings made of special steel, which can be producedcost-effectively and can be employed in actual use.

This and other objects are attained in accordance with one aspect of theinvention directed to a process for producing press fittings, inparticular press fittings made of steel, particularly special steel,starting with blanks with at least one pipe end. The pipe end isreceived in a die and is widened with the aid of a mandrel is pushed inthe axial direction into the pipe end. Then, the pipe end is axiallyupset in the same die in order to bend an annular area of the pipe endradially outward into an annular groove formed in the die.

Steel pipes from which sections are cut to size are the basis forproducing the press fittings. The cut-off pipe sections are convertedinto a press fitting in an integrated step with two partial steps,wherein the two partial process steps are designed in such a way thatthey can be performed one after the other without an intermediate stepin a single die.

For producing the press fittings, the cut to size pipe sections arewidened and provided with an annular bead, which is used as an O-ringseat. Widening and beading (i.e. the formation of the bead) thereforetakes place in one continuous operation, so to speak. It is notnecessary to either transport the press fitting to another die, or toperform intermediate work, for example finish calibration or cutting tosize, between the two partial process steps. Therefore the series ofsteps consists of cutting to size, widening, and application of thebead. Because of the possible combination of widening and beadapplication into a conversion step which can be performed in a singleprocessing station, the processing machine can make do with a reducednumber of processing stages. The combination of widening and beadapplication permits a quite considerable reduction of construction andstructural outlay at the machine for producing press fittings which, inthe end, is reflected in a considerable cost reduction of the specialsteel press fittings. It has been shown on the other hand that, in spiteof the omission of intermediate calibration between widening and beadapplication, i.e. in spite of the combination of the two individualsteps into an integrated process step, it is possible to produce thedesired press fittings with the required dimensional accuracy andquality, so that faultless pipe connections can be produced from themass-produced press fittings.

In the process, the diameter of the pipe end of the blank is preferablywidened by more than twice the wall thickness. This creates thepossibility to start out with a blank which had been cut to size fromthe pipe materials of the type which is to be connected by means of thepress fittings in the course of the later installation. Therefore nospecial pipe material is required for producing the press fittings,which in turn lowers the costs and simplifies production. Moreover,widening of the pipe end has the effect that an insertion end, whichlimits the axial insertion depth of the pipe to be connected, is formedon the press fitting to be produced. This creates defined conditions, sothat the beaded connection to be made is given the required axialtensile strength.

For executing the process, a mandrel for widening the pipe end of theblank is initially pushed axially into the latter under pressure. In thecourse of this, the conical front end of the mandrel widens the pipeend, which is stretched in the circumferential direction and thereforerests against the outer cylindrical surface of the mandrel with aradially inward directed force. The exterior diameter of the mandrel andthe interior diameter of a corresponding section of a mold receiving theblank are matched to each other in such a way that now the wall of thewidened blank rests, at least almost, against the interior wall of themold. During the process step now following, which can chronologicallyoverlap, i.e. start with the widening step, the pipe end is subjected toan upsetting axial force, for example by means of an annular shoulderprovided in the mandrel, or by a separate pressure sleeve. This occurssurprisingly, in spite of an inward directed pretension, because of theaxial upsetting force the material of the wall of the pipe end bulgesoutward in an annular area into an annular groove provided in the mold,wherein the special steel material is still further stretched in thecircumferential direction than had occurred in the widening step. Tomake this possible in the represented manner, a special steel materialof high tensile strength and toughness is required. The special steelmaterial often employed in water line installations meets theserequirements.

The process is suitable for producing the press fittings by startingfrom welded pipe material. It is possible that a surface can exist inthe area of the weld seam produced in the course of a laser weldingprocess, for example, which is not suitable for a tight seating of anO-ring. This can be the case in particular if the pipe material waswelded from the outside. Relief can be provided here in that anintermediate processing, particularly of the weld seam, takes placefollowing the upsetting step. This can take place in a rolling process,for example, in that the weld seam area in particular is rolled overseveral times from the inside. For example, a so-calledroller-burnishing process is performed as the rolling process, wherein aroller supported on a finger and rotatably seated is introduced into thepipe end and is rolled along the formed bead on an orbital track.Preferably several thousand, preferably more than ten thousandrepetitions are performed here, in which the roller is pushed radiallyoutward. The weld seam area in particular is smoothed here. It isalternatively possible to grind the annular groove. In this connectionit might possibly be sufficient to grind over only the weld seam area.While the roller-burnishing process has the advantage of closing poresand pits by pushing them closed, with the grinding process it ispossible to achieve particularly short clock cycles and particularlygood bead geometries.

The press fittings to be created can have one, two, three or more pipeends—depending on their employment. The simplest employment is astraight pipe connector with two pipe ends. Cover plates only have onepipe end. Branch elements can have three or more pipe ends, wherein theblanks of such branchings are produced in a preparatory work step insuch a way that appropriate straight pipe ends are provided in thedesired amounts. If curved fittings are to be produced, a pipe section,which was cut to size, is initially bent in an appropriate mold, afterwhich the above discussed process steps are performed.

The device suited for producing press fittings has a combined wideningand upsetting station, part of which are at least a multi-part die, awidening mandrel and the upsetting element. The widening mandrel and theupsetting element can be combined into one element, or can be separatelyembodied. Both elements, the widening mandrel and the upsetting element,are employed in the same die (mold) simultaneously or one after theother. The combined widening and upsetting station therefore is a singleprocessing station, in which widening, as well as beading, is performedwithout intermediate steps. Widening and beading in a single processingstation allows a particularly cost-effective, but yet precise productionof press fittings, i.e. the mass production of the press fittings of aquality which permits the dependable production of press connectionswhich remain tight over a long period of time.

The die preferably has a receiving chamber with several sections, i.e.at least one first and one second section, which are of differentdiameters and make a transition into each other at an annular shoulder.The diameter of the first section preferably matches the exteriordiameter of the not yet widened blank, while the blank in the secondsection should approximately correspond to the exterior diameter of theblank after the widening step. The annular shoulder formed between thefirst and second sections is used for defining the exterior shape of thepress fitting in the transition between its not yet widened to itswidened area. The annular shoulder can additionally be used as thestroke limitation for the widening mandrel, in particular if its strokedepth is not fixed by its drive mechanism.

The die can be divided parallel in relation to the longitudinaldirection of the pipe end, or transversely to the latter. With paralleldivision, the die (the mold) is constituted by two mold halves, whoseseparating line lies substantially on a level with the center line ofthe blank. The annular groove formed in the mold halves for defining theexterior shape of the bead to be formed is provided in both mold halvesand its axial extension cannot be changed. In contrast to this, thetransverse division of the mold half permits the application of aseparating line centrally in respect to the annular groove, so that theaxial extension of the annular groove can be changed. In this case it isparticularly advantageous to move the mold in the course of the wideningor upsetting process in such a way that the annular groove slowlycloses, i.e. its axial extension is reduced from a larger size to thedesired size. By means of this it is possible to initially bulge alarger area of the pipe wall outward, because of which the bulging wallpossibly molds itself better to the shape of the annular groove.However, it is essential for the annular groove to be closed before wallmaterial has penetrated too far outward, i.e. into the gap between themold halves.

It is possible to combine the widening mandrel and the upsetting elementby forming an annular shoulder on the widening mandrel. There, theupsetting element and the widening mandrel always run synchronously inregard to each other, which results in a high degree of processdependability and a simple die. However, if required, the upsettingelement can also be a separately driven pressure sleeve, which isdisplaceably seated on the mandrel, which is placed on the pipe end andupsets it after the pipe end has been completely widened. It is possiblehere to operate the pressure sleeve in a travel-controlled orforce-controlled manner, for example, in order to achieve optimumproduction results. Anyway, the stroke of the pressure elements isdimensioned in such a way that the material of the pipe end in the areaof the annular groove bulges outward, but is not pushed together into aflat disk flange. This is preferably achieved by a travel control of thepressure element. However, the widening mandrel can be connected to itsdrive mechanism for example by means of an interposition of a relativelystrong spring, so that it runs up resiliently against the annularshoulder between the first section and the second section of the die.

The device can be additionally provided with a roller-burnishingstation. The latter can be arranged in a separate processing station ifa very rapid work cycle is desired. However, it is preferred tointegrate the roller-burnishing station also into the widening andupsetting station. A roller, rotatably seated on a finger, as well as adrive mechanism, are part of the roller-burnishing station, by means ofwhich the finger is inserted into the widened and beaded pipe end and ismoved in a circular manner until the formed bead has the desired shape,particularly in the area of a possibly existing weld seam on the pipewall. A grinding station can also be provided in place of theroller-burnishing station.

It is possible by means of the process and the device to produce pressfittings of special steel which have a widened pipe end and an annularbead in it for receiving an O-ring as a sealing element. The specialfeature of these special steel press fittings resides in thatpipe-shaped crimped areas of identical diameter and approximately thesame axial length are provided on both sides of the O-ring, i.e. theannular bead, which can be used as crimping area. With these, thespecial steel press fitting is pressed on both sides of the O-ringtogether with a pipe end, which is to be connected. This not onlyactually increases the assembly dependability and the solidity of theconnection, but also the acceptance in the market place, and moreoverpermits the employment of crimping tools such as have so far been usedfor copper press fittings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1, a schematic sectional view of a device for producing pressfittings, having a die, a mandrel and an upsetting element, during thewidening step and prior to upsetting,

FIG. 2, a schematic sectional view of the die in FIG. 1 at the end ofthe widening step and the upsetting step,

FIG. 3, the die in FIG. 1 during the roller-burnishing process,

FIG. 4, a schematic sectional view of a modified embodiment of a devicefor producing press fittings in the course of the widening step,

FIG. 5, a simplified and schematic sectional view of the device in FIG.4 at the end of the widening and upsetting step,

FIG. 6, a schematic sectional view of a further embodiment of a devicefor producing press fittings in the course of the widening step,

FIG. 7, a schematic sectional view of the device in FIG. 6 afterwidening and upsetting,

FIG. 8, a schematic sectional view of a further embodiment of the deviceof the invention, having a movable die, during the upsetting process,

FIG. 9, a schematic sectional view of the device in FIG. 8 at the end ofthe two processing steps (widening and upsetting), and

FIG. 10, a schematic sectional view of a finished special steel pressfitting for connecting two special steel pipes.

DETAILED DESCRIPTION OF THE DRAWINGS

A device 1 is illustrated in FIG. 1 for producing press fittings, suchas can be seen in FIG. 10 in the form of a straight press fitting 2, forexample. The device 1 in FIG. 1 is used for producing curved pressfittings, which are based on pre-bent, cut to size and pipe-shapedblanks 3 of constant interior and exterior diameters.

The device 1 has a mold or die 5, which is held on a base 4 and can bedivided and encloses a receiving chamber 6 with a first section 7 and asecond section 8. The first section 7 of the receiving chamber 6 has aninterior diameter which matches the exterior diameter of the blank 3.The second section 8 is used for receiving a pipe end 9 of the blank 3,which will constitute the later crimping area of the press fitting to beformed. The interior diameter of the substantially cylindrical secondsection 8 of the receiving chamber 6 is greater than the exteriordiameter of the non-deformed pipe end 9. The interior diameter of thesecond section 8 is preferably greater by twice the wall thickness ofthe pipe end 9 than the exterior diameter of the non-deformed pipe end9. A conical annular shoulder 11 connects the two sections 7, 8 of theinterior chamber 6. An annular groove 14, which fixes the exteriorcontour of an annular bead 15 to be formed on the press fitting 2 isformed at some distance from the annular shoulder 11 and preferably atan even greater distance from the open end 12 of the receiving chamber6. The annular groove 14 forms a closed ring of a constant,approximately semicircular cross section.

The die 5 illustrated in FIG. 1 is divided parallel in respect to alongitudinal direction 16 of the receiving chamber 6. The longitudinaldirection 16 matches the two axial directions of the open pipe ends ofthe blank 3.

A widening mandrel 18, an upsetting element 19 and a drive mechanism 21belong to the die 5. The widening mandrel 18, the upsetting element 19,the drive mechanism 21 and the die 5 constitute a combined widening andupsetting station of the device 1.

The widening mandrel 18 is a cylindrical element provided with a bezel23 on its front face, whose exterior diameter is slightly larger thanthe exterior diameter of the not yet widened pipe end 9. The bezel 23defines a conical annular face, whose diameter directly adjoining thefront face of the widening mandrel 18 is less than the interior diameterof the not yet widened pipe end 9. The bezel 23 includes an acute angleof taper of such a size, that the widening mandrel 18 can be insertedinto the pipe end 9 while widening it, and without compressing the pipeend 9 in front of it. The length of the widening mandrel 18 is greaterthan the distance between the annular shoulder 11 and the annular groove14.

The widening mandrel 18 is connected rigidly and, if desired, as onepiece with the upsetting element 19 which, in the embodiment in FIG. 1,is constituted by a cylinder body, which makes a transition via a step-or annular shoulder-like transition 25 into the cylindrical wideningmandrel 18. The cylinder body has an exterior diameter which exceeds theinterior diameter of the widened pipe end 9. The exterior diameter ofthe cylinder body is preferably less than the interior diameter of thesecond section 8 of the interior chamber 6, so that the mandrel, or thebody constituted by the widening mandrel 18 and the cylinder body, canenter into the second section 8 of the receiving chamber 6.

The drive mechanism 21 which, in the present exemplary embodiment isconstituted by an hydraulic drive mechanism, is used for actuating andmoving this combined widening and upsetting mandrel. Part of this is apiston 26, which divides a cylinder chamber 27 into a work chamber 28 aand a further work chamber 28 b. The piston 26 is connected with thewidening mandrel 18 and the upsetting element 19, for example via apiston rod 29. Fluid channels, not represented in detail, are used forthe selective charging of the work chambers 28 a, 28 b with hydraulicfluid under pressure. By means of this the piston rod 29 can bespecifically moved in both axial directions respectively in thedirection of the arrows 31, 32.

The device 1 described so far operates as follows:

Cut to size and pre-bent pipe-shaped blanks 3 of constant diameter arethe basis. These are placed into the die 5, after which the die isclosed. The blank 3 extends with its pipe end 9 into the section 8 ofthe receiving chamber 6, but does not rest against the die 5. The blank3 is axially fixed in the die 5 by means of its curvature. The mandrel18 is in its farthest possible right position in FIG. 1 and is not yetin contact with the pipe end 9. Now the work chamber 28 b is chargedwith fluid, so that the piston 26, and with it the piston rod 29, theupsetting element 19 and the widening mandrel 18 are moved toward thedie 5, as indicated by the direction of the arrow 31. In the course ofthis, the widening mandrel 18 is placed with its bezel 23 on the frontface of the pipe end 9, which has been preferably deburred and, ifrequired, provided with a slight inner and outer bezel. Because of thecontinued axial movement of the widening mandrel 18, it penetrates thepipe end 9 and widens it in the process, but does not substantiallycompress it. A certain shortening of the pipe end 9 can occur because ofthe now appearing stretching of the wall of the pipe end 9 in thecircumferential direction. The widened pipe end 9 rests under tensionagainst the surface of the widening mandrel 18. The latter continues toslide further into the interior chamber of the pipe end and widenslonger and longer sections of the pipe end. Before the bezel 23 reachesthe annular shoulder 11, the upsetting element 19, i.e. the appropriatestep 25 (annular shoulder) is placed on the front face 9 a of the pipeend 9. In the course of the further movement of the piston 26, the pipeend 9 is now upset, because of which the wall of the pipe end 9spontaneously bulges outward in the area of the annular groove 14against its own, radially inward directed pretension. This takes placeover the entire circumference. The length of the upsetting stroke isdimensioned in such a way that the upsetting process is terminated oncethe wall of the pipe end 9 completely rests in the annular grove 14.This is illustrated in FIG. 2. The upsetting stroke is approximately aslong as the difference between the wall length of the annular bead andthe axial length thereof.

The length of the stroke can be dimensioned by an appropriate design ofthe drive mechanism 21, for example in that the piston stroke iscorrespondingly limited. When the work stroke is terminated, i.e. thepipe end 9 is widened and upset, as illustrated in FIG. 2, the pressurein the work chamber 28 b is relieved and the work chamber 28 a ischarged with pressure, so that the piston 26, and with it the upsettingelement 19 and the widening mandrel 18 are moved out of the die 5 in thedirection of the arrow 32 and release the now produced press fitting.The latter can now be removed from the mold 5 in that the latter isopened and a fresh blank 3 is inserted, after which the above explainedwork process is repeated. Therefore only a single piston stroke of thepiston 26 is required for producing the press fitting. Production iseffective and precise.

For the case wherein the blank 3 was cut to size from a welded pipe inparticular, it is recommended to add a further work step, which can beperformed in the same die 5, or in a separate die. In the exampleillustrated in FIG. 3, the first mentioned option is exercised. Theupsetting of the blank 3 has already been finished and it still remainsin the mold 5 for the roller-burnishing step. A roller-burnishing device34 is used for performing the roller-burnishing step. Part of the latterare a finger-like support 35, on whose free end a roller 36 is rotatablyseated, whose diameter is clearly less than the interior diameter of thewidened pipe end 9. The support 35 is connected with a drive andpositioning device 37 which is arranged for placing the roller 36against the wall. Then the support is moved so that the roller 36 is runinto the interior of the pipe end 9 and is then moved in the radialdirection in such a way that the roller 36 performs a circumferentialmovement in the annular bead 15 which had been formed. For example, theroller-burnishing process is performed for a length of 2 to 4 seconds ata number of revolutions of more than 5000 rpm. In this way more than 100rotations result, which cause the sufficient smoothing of the inside ofthe annular bead, in particular in the area of a possible weld seam. Itis alternatively possible to provide a driven grinding disk in place ofthe roller 36, which grinds over the entire annular bead 15, or only thearea of the weld seam.

A modified embodiment of the device 1 is illustrated in FIG. 4. To theextent that the device 1 agrees with the device in FIG. 1, the samereference numerals are employed and reference is made to the descriptionabove.

In contrast to the previously described device 1, the device 1 in FIG. 4has a drive device 21 with separate drive mechanisms 21 a, 21 b for thewidening mandrel 18 and the upsetting element 19. On its side remotefrom the bezel 23, the widening mandrel 18 is provided with a blind bore40, which houses a compression spring 41. The latter is supported on thebottom of the blind bore 40. A piston rod 42 of a hydraulic piston 43dips into the blind bore 40. The piston is arranged in a hydrauliccylinder 44 and there separates two work chambers 45 a, 45 b. By meansof a specific charging of the work chambers 45 a, 45 b with pressure,the widening mandrel 18 can be moved in both directions 31, 32. In thiscase the stroke of the piston 43 is so great that the widening mandrel18 can run up against the annular shoulder 11. The latter is used as astroke limitation for the piston 18. The spring 41 is so stiff that inthe course of the widening mandrel 18 entering the pipe end 9 the springis not at all, or only slightly, compressed. This causes a preciseformation of the diameter transition of the blank 3 from the widenedpipe connector area 9 to the not widened area. Moreover, the device 1becomes insensitive to positioning tolerances between the die 5 and thedrive device 21.

A further special feature of the embodiment of the device 1 illustratedin FIG. 4 resides in the upsetting element 19. The latter is embodied asa sleeve, which is displaceably seated on the widening mandrel 18. Thesleeve is provided with its own drive mechanism 21 a, part of which is apiston 47 seated in a cylinder 46. The latter separates two workchambers 48 a, 48 b, which can be selectively and specifically chargedwith hydraulic fluid. In this way the sleeve can be specifically movedin the direction of the arrows 31, 32 in order to contact the front face9 a of the pipe end 9 with its own front face and to upset the pipe end9. The two drive mechanisms 21 a, 21 b can be controlled independentlyfrom each other, by means of which the widening and upsetting of thepipe end 9 can be optimized. This embodiment has particular importancewhere the dies 5 must often be changed in a machine in order to be ableto produce different press fittings.

While FIG. 4 illustrates the widening of the pipe end 9, FIG. 5represents the status of the device 1 at the termination of theupsetting step. The widening mandrel 18 has pressed the pipe wall firmlyagainst the inner shoulder 11. The pipe end 9 is completely widened andthe sleeve has dipped into the die 5 and has upset the pipe end 9 tosuch an extent that the pipe wall just fills the annular groove 14, andtherefore the desired bead 15 has been formed.

A further embodiment of the device 1 is illustrated in FIG. 6. To theextent that there is agreement with the previous embodiments, referenceis made, based on the same reference numerals, to the above description.

In contrast to the above described embodiments, the die 5 of the device1 is not only divided into two, but into three. In addition to adivision parallel with the longitudinal center axis 16, it is divided ina plane located in the annular groove 14. Thus, a die element 5 aexists, which can be placed against the remaining die 5 prior to, duringor after upsetting. An appropriate cylindrical seat 50 is used forcentering. The die element 5 a is preferably attached to the seat 50 ofthe die 5 prior to the commencement of the upsetting step. For thispurpose, the die element 5 a is moved toward the die 5 in the directionof the arrow 31 by means of an appropriate positioning device. Thepositioning device furthermore supports the drive device 21 foractuating the widening mandrel 18 and the upsetting element 19. Onceboth process steps, i.e. widening and upsetting, have been performed,the device 1 is in the status illustrated in FIG. 7. Now the piston 26is retracted out of the pipe end 9 by charging the work chamber 28 awith pressure. Thereafter the die element 5 a is moved away from the die5 in the direction of the arrow 32. By means of this the pipe end 9 ispartially freed. After opening the remaining die 5, the press fitting 3can now be removed. The advantage of this embodiment rests in that thedie element 5 a maintains the two other elements of the die 5 togetherat the seat 50, and that in this case a precisely operating die can beconstructed in a simple way, in particular in the area of the annulargroove 14.

A modified embodiment of the device 1 illustrated in FIGS. 6 and 7 isrepresented in FIGS. 8 and 9. While in the previously describedembodiment (FIGS. 6 and 7) the widening mandrel 18 and the upsettingelement 19 were movably guided and driven in relation to the die element5, the widening mandrel 18 in the embodiment of the device 1 in FIGS. 8and 9 is rigidly maintained on the die element 5 a, and the upsettingelement 19 is embodied as an annular pressure face 25′ on the dieelement 5 a. The latter as a whole is connected with a drive device, notfurther represented, and is specifically movable in the direction of thearrows 31, 32.

Adjacent its half 14 b of the annular groove 14, whose other half 14 ais housed in the remaining die 5, the die element 5 a has a bore 52which, at a defined distance from the annular groove half 14 b, isreduced to the diameter of the widening mandrel 18. The latterpenetrates the rest of the bore 52. On its end it is provided with anend plate 18′, which is braced by the die element 5 a against anabutment 53. The unit of the abutment 53, the die element 5 a and thewidening mandrel 18 formed in this way can be moved as a whole towardthe die 5 and away from it by means of the drive device. The distancebetween the annular face 25′ and the annular groove 14 is again of sucha size that, when the mold 5, 5 a is closed, the widened pipe end 9 isupset to such an extent that the bulging pipe wall just fills theclosing annular groove 14. This is illustrated in FIG. 9. Here, the workis performed by means of a mold with a total of three elements and asingle drive device for the widening mandrel 18, as well as for theupsetting element 25′.

It is possible to produce press fittings 2, such as illustrated by wayof example in FIG. 10, by means of the above described devices and thecorresponding process. Such a special steel press fitting is producedfrom a welded piece of pipe, whose weld seam 60 is schematicallyillustrated in FIG. 10. It has one, two or more pipe connecting areas61, 62, all of which are embodied to be hollow-cylindrical. Each pipeconnecting area 61, 62 has two hollow-cylindrical sections 61 a, 61 b,62 a, 62 b, between each of which the annular bead 15 is arranged. Thetwo cylindrical sections 61 a, 61 b, 62 a, 62 b have the same interiordiameter. They constitute crimping areas for the connection of pipes.The pipes to be connected are then mechanically connected to both sidesof the respective O-ring 63 with the press fitting 2.

The disclosed process permits the production of special steel pressfittings practically in a single work step, which comprises two processsteps, which can be performed simultaneously, or also one after theother. The cut to size blank is widened in a die and is upset in orderto form the desired pipe connection areas 61, 62. The process has beenshown to be dependable for special steel press fittings. Otherpressure-resistant and tough metals can also be employed. The process isparticularly suitable in connection with a following roller-burnishingstep or grinding step for producing press fittings from welded specialsteel pipes.

1. A process for producing a press fitting, starting with a blank havinga pipe end, comprising a first process step which includes receiving thepipe end in a die and widening the pipe end with the aid of a mandrel,having an exterior diameter that exceeds the interior diameter of thepipe end, by pushing the mandrel in the axial direction into the pipeend, and comprising a second process step which includes axiallyupsetting the pipe end in the same die as a separate consecutive stepimmediately following the first process step in order to bend an annulararea of the pipe end radially outward into an annular groove formed inthe die.
 2. A process for producing press fittings in accordance withclaim 1, characterized in that in the first process step the diameter ofthe pipe end is widened by more than twice the wall thickness of thepipe end.
 3. A process for producing press fittings in accordance withclaim 1, characterized in that the mandrel, which had been moved intothe pipe end in the first step remains in the pipe end during theexecution of the second process step.
 4. A process for producing pressfittings in accordance with claim 1, characterized in that the blank isproduced from a welded special steel pipe.
 5. A process for producingpress fittings in accordance with claim 1, characterized in that a cutto size piece from a welded pipe is used as the blank.
 6. A device (1)for producing a press fitting, starting with a blank having (3) a pipeend (9), said device comprising a combined widening and upsettingstation (22), which includes at least the following elements: amulti-part die (5) having a receiving chamber (6) for the blank (3),wherein the receiving chamber (6) for the blank (3) has at least onesection (7) of the same diameter as the blank (3), and a second section(8) of an interior diameter which is greater than the exterior diameterof the pipe end (9), wherein the second section (8) has an annulargroove (14) on its interior face in order to fix the exterior shape ofan annular bead to be formed on the pipe end (9), a widening mandrel(18), which is guided to move axially into the second section (8) of thereceiving chamber (6) and out of it, is connected with a drive device(21), and having an exterior diameter that exceeeds the interiordiameter of the pipe end (9), but is less than the interior diameter ofthe section (8) into which the widening mandrel (18) is to be moved, sothat an annular space is defined between the widening mandrel (18) andthe interior face of the second section (8), having a radial thicknessthat approximately corresponds to the wall thickness of the pressfitting (3), and an upsetting element (19), which is guided so that itmoves axially toward the annular groove (14) of the die (5) and awayfrom it and is connected with the drive device (21) and has an annularpressure face (25) which is designed to be brought into contact with thepipe end (9) and to upset the pipe end (9), the upsetting element (19)being operatively arranged and dimensioned so that the annular pressureface (25) upsets the pipe end to form the annular bead as a separateconsecutive step after the pipe end is widened in the second section bythe widening mandrel.
 7. The device in accordance with claim 6,characterized in that the interior chamber (6) of the die (5) has anannular shoulder (11) between the first section (7) and the secondsection (8).
 8. The device in accordance with claim 6, characterized inthat the die (5) is embodied in two parts and is divided along a facewhich is arranged parallel to the longitudinal pipe direction (16) ofthe press fitting (2).
 9. The device in accordance with claim 6,characterized in that the die (5) is divided transversely in respect tothe longitudinal pipe direction (16) of the blank (3).
 10. The device inaccordance with claim 9, characterized in that a portion (5 a) of thedie (5) is rigidly connected with the widening mandrel (18), as well aswith the upsetting element (19).
 11. The device in accordance with claim6, characterized in that the widening mandrel (18) is connected with adrive mechanism (21 b) by a spring (41).
 12. The device in accordancewith claim 6, characterized in that the widening mandrel (18) is rigidlyconnected with its drive device (21).
 13. The device in accordance withclaim 6, characterized in that the widening mandrel (18) is rigidlyconnected with the upsetting element (19), and the drive device (21) forthe widening mandrel (18) simultaneously constitutes the drive device(21) for the upsetting element (19).
 14. The device in accordance withclaim 6, characterized in that the upsetting element (19) and thewidening mandrel (18) have drive mechanisms (21 a, 21 b), which areindependent of each other.
 15. The device in accordance with claim 6,characterized in that the device additionally has a roller-burnishingdevice (34).
 16. The device in accordance with claim 6, characterized inthat the device additionally has a grinding station with a grindingdisk, which can be moved into the pipe end (9) and can be placed in aradial movement into the annular bead (15) in order to perform agrinding operation in the latter.